According to the agenda-setting theory, propounded by Maxwell McCombs and Donald Shaw in the 1970s, mass media set the agenda for public opinion by highlighting certain issues. Studying the way political campaigns were covered in the media, Shaw and McCombs found the main effect of news media to be agenda-setting, telling people not what to think, but what to think of. Agenda setting is usually referred to as a function of mass media and not a theory (McCombs & Shaw, 1972).

The theory explains the correspondence between the rate at which media cover a story and the extent that people think that this story is important. This correspondence has repeateadly been shown to occur.

Agenda-setting is believed to occur because the press must be selective in reporting the news. News outlets act as gatekeepers of information and make choices about what to report and what not. What the public know and care at any given time is mostly a product of media-gatekeeping.

The agenda-setting function is a 3 part-process:

#Media Agenda - issues discussed in the media #Public Agenda - issues discussed and personally relevant to the public #Policy Agenda - issues that policy makers consider important

One of the debates between researchers is the questions of causality: does the media agenda cause the public agenda, or vice-versa Iyengar and Kinder established causality with an experimental study where they identified that priming, vividness of presentation and position were all determinants of the importance given to a news story. However, the question of whether there is an influence of the public agenda on the media agenda is open to question.

== History ==

The basic ideas of the theory can be traced back to the work of Walther Lippmann, a prominent American journalist. Lippmann (1922) proposed that people did not respond directly to events in the real world but lived in a pseudo-environment composed of the pictures in our heads . The media would play an important part in the furnishing of these pictures and shaping of the pseudo-environment. The basic premise of the theory in its modern form, however, was first formulated by Bernard Cohen (1963): [The press] may not be successful much of the time in telling its readers what to think, but it is stunningly successful in telling its readers what to think about (p.13).

== Important Concepts ==

==== See also ====

*Agenda Setting Conference by the Media Tenor Institute

= References =

== Secondary ==